Capital Ratios (Schedule Of The Total Risk-based, Tier 1 Risk-based And Tier 1 Leverage Requirements) (Details)	Sep. 30, 2020	Dec. 31, 2019
Franklin Financial Services Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Risk-based Capital Ratio: Ratio	14.21%	14.82%
Tier 1 Risk-based Capital Ratio: Ratio	14.21%	14.82%
Total Risk-based Capital Ratio: Ratio	17.62%	16.08%
Tier 1 Leverage Ratio: Ratio	8.75%	9.72%
Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Risk-based Capital Ratio: Ratio	13.99%	14.62%
Common Equity Tier 1 Risk-based Capital Ratio: Adequately Capitalized Minimum: Ratio	4.50%
Common Equity Tier 1 Risk-based Capital Ratio: Well Capitalized Minimum: Ratio	6.50%
Tier 1 Risk-based Capital Ratio: Ratio	13.99%	14.62%
Tier 1 Risk-based Capital Ratio: Adequately Capitalized Minimum: Ratio	6.00%
Tier 1 Risk-based Capital Ratio: Well Capitalized Minimum: Ratio	8.00%
Total Risk-based Capital Ratio: Ratio	15.25%	15.87%
Total Risk-based Capital Ratio: Adequately Capitalized Minimum: Ratio	8.00%
Total Risk-based Capital Ratio: Well Capitalized Minimum: Ratio	10.00%
Tier 1 Leverage Ratio: Ratio	8.61%	9.59%
Tier 1 Leverage Ratio: Adequately Capitalized Minimum: Ratio	4.00%
Tier 1 Leverage Ratio: Well Capitalized Minimum: Ratio	5.00%

Tangible Capital Required For Well Capitalized To Tangible Assets

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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The minimum amount of Tangible Capital divided by tangible assets (Tangible Capital Ratio) as defined in the regulations.

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Tangible Capital divided by Tangible assets as defined in the regulations.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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